レイリー・ベナール・ポアズイユ乱流における熱・運動量輸送

抄録

The onset of thermal convection and its effects on heat and momentum transfer have been investigated numerically in pressure-driven turbulent flow in a horizontal plane channel heated from below. At fixed values of the Reynolds number, Re = 2000, 3000, 4000, 6000, the bulk Richardson number Ri is gradually increased to inspect the effects of buoyancy on the wall-bounded turbulent shear flow. Buoyancy-induced streamwise rolls are observed to critically appear at distinct values of the Richardson number depending on the Reynolds number. It is found that the onset of thermal convection can be identified at the critical turbulence Grashof number Gr_T = 4Ri/C_f² ≅ 200 being independent of Re, where C_f is the skin friction coefficient. At Re = 2000, moreover, after the onset of the convection Gr_T > 200 the Stanton number, i.e. dimensionless wall heat flux, is observed to increase due to heat transfer enhancement of the convection with increasing Ri, while the skin friction coefficient decreases in a specific range of Ri.